1. Field of the Invention
The present invention relates to a wet type image forming apparatus. More particularly, the present invention relates to a paper discharge guide unit for guiding a printing paper passed through a fusing unit toward a pair of discharging rollers in a wet type electrophotographic image forming apparatus.
2. Description of the Related Art
In general, a liquid toner used for a wet type electrophotographic image forming apparatus is composed of toner particles and a liquid that is used as a carrier of the toner particles. The carrier liquid contains volatile organic compounds. Therefore, when a printing paper, onto which a predetermined image developed by the liquid toner in an image forming unit of the wet type electrophotographic image forming apparatus was transferred, passes through a fusing unit, some of the volatile organic compounds of the liquid toner are evaporated by the heat and pressure of the fusing unit and some of the resultant gaseous compounds soak into the printing paper. When the printing paper is being discharged from the fusing unit outside the wet electrophotographic image forming apparatus (hereinafter referred to as a wet image forming apparatus), the volatile organic compound gases, which soaked into the printing paper in the fusing unit, are emitted from the printing paper. If the gases are not fully emitted before the paper is discharged from the printer, the gases are emitted to the atmosphere. Also, if the wet image forming apparatus cannot treat all of the captured gases, untreated volatile organic compound gases enter the atmosphere. The volatile organic compound gases are a pollutant, and may cause users to feel ill. Furthermore, environmental protection laws may restrict the emission of the gases. Therefore, wet image forming apparatuses have various types of paper discharging units to absorb and remove all of the volatile organic compound gases that are soaked in the printing paper before the printing paper is discharged to the atmosphere. An example of one such paper discharging units is shown in FIG. 1.
Referring to FIG. 1, a conventional paper-discharging guide unit 1 has a discharge guide plate 10 and an air absorbing portion (not shown). The discharge guide plate 10 has a guide frame 11 and a plurality of guide ribs 13. The guide frame 11 is formed in the shape of a hollow rectangle, namely, a shape similar to a rectangular window frame. The plurality of guide ribs 13 are located inside the frame. The plurality of guide ribs 13 are disposed inside the guide frame 11 and are parallel to the direction of movement of a printing paper P passing above the discharge guide plate. Therefore, there are a plurality of spaces between the guide frame 11 and the plurality of guide ribs 13 of the discharge guide plate 10.
The air-absorbing portion is disposed below the discharge guide plate 10 to absorb air from the plurality of spaces between the guide frame 11 and the plurality of guide ribs 13. The air-absorbing portion is comprised of a duct (not shown) that is fluidly connected to the guide frame 11 and an absorbing fan (not shown) that generates a suction force.
The operation of the paper-discharging guide unit 1 to remove volatile organic compound gases from the printing paper being discharged will now be explained.
When the printing paper P passed through the fusing unit (not shown) moves onto the discharge guide plate 10, the absorbing fan (not shown) of the air-absorbing portion operates and thereby generates the suction force. The suction force is applied to the printing paper P moving on the discharge guide plate 10 through the plurality of spaces between the guide frame 11 and the plurality of guide ribs 13 of the discharge guide plate 10. The volatile organic compound gases, which are emitted from the printing paper P or are soaked in the printing paper P, are absorbed into the air-absorbing portion. The printing paper P with the volatile organic compound gases removed is discharged outside of the wet image forming apparatus. The volatile organic compound gases absorbed by the air-absorbing portion are decomposed into harmless gases by an exhaust gas decomposing apparatus (not shown) and then are exhausted to the atmosphere.
The paper-discharging guide unit 1 described above may cause problems, however. First, the suction force may generate an uneven flow of the volatile organic compound gases and/or of air may in the plurality of spaces 15 between the guide frame 11 and the plurality of guide ribs 13. Due to the flow, the suction force may not be uniformly applied to the printing paper P moving above the discharge guide plate 10. When the suction force is not uniformly applied to the printing paper P, one or both corner of a leading end of the printing paper P may be bent in the direction of the suction force. When the printing paper P having one or both bent corners passes through a pair of discharging rollers (not shown), one or both corners of the printing paper P are folded.
Second, the suction force is not applied to the area of the printing paper P that touches the plurality of guide ribs 13 because the plurality of guide ribs 13 block the suction force. And, since the plurality of guide ribs 13 is disposed parallel to the discharge direction of the printing paper P, the suction force is not applied to the area 19 of the printing paper P that touches the plurality of guide ribs 13. In other words, while the printing paper P is moving from S1 position to S2 position, the area 19 of the printing paper P that touches the plurality of guide ribs 13 continuously contacts the plurality of guide ribs 13. Therefore, the volatile organic compound gases soaked in the area 19 of the printing paper P are not absorbed by the air-absorbing portion and remain in the paper. In the worst case, the volatile organic compound gases emitted from the area 19 of the printing paper P condense into a liquid between the plurality of guide ribs 13 and the printing paper P, and the liquid contaminates the printing paper P.
Accordingly, there is a need for a wet image forming apparatus with an improved apparatus for removing volatile organic compound gases soaked in paper.